5,845 research outputs found

    Determination of mass of IGR J17091-3624 from "Spectro-Temporal" variations during onset-phase of the 2011 outburst

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    The 2011 outburst of the black hole candidate IGR J17091-3624 followed the canonical track of state transitions along with the evolution of Quasi-Periodic Oscillation (QPO) frequencies before it began exhibiting various variability classes similar to GRS 1915+105. We use this canonical evolution of spectral and temporal properties to determine the mass of IGR J17091-3624, using three different methods, viz : Photon Index (Γ\Gamma) - QPO frequency (ν\nu) correlation, QPO frequency (ν\nu) - Time (day) evolution and broadband spectral modelling based on Two Component Advective Flow. We provide a combined mass estimate for the source using a Naive Bayes based joint likelihood approach. This gives a probable mass range of 11.8 M⊙_{\odot} - 13.7 M⊙_{\odot}. Considering each individual estimate and taking the lowermost and uppermost bounds among all three methods, we get a mass range of 8.7 M⊙_{\odot} - 15.6 M⊙_{\odot} with 90% confidence. We discuss the probable implications of our findings in the context of two component accretion flow.Comment: 10 pages, 5 figures (4 in colour), 2 tables. Accepted for publication in Ap

    Measuring Spillovers from Alternative Forms of Foreign Investment

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    Much of the endogenous growth literature has dwelled on evaluating the spillover effects of trade on growth, but much less efforts have been directed towards tracing and quantifying the spillover effects of foreign investments. This paper, in incorporating the effects of various types of foreign investments, namely foreign direct investment (FDI), foreign portfolio investment (FPI) and other foreign investment (OFI) fills this gap in the literature. Adopting the stochastic frontier approach, this paper constructs an OECD frontier based on a panel dataset of 20 OECD countries over the 1981-2000 period. Spillover effects of FDI, FPI, OFI and trade are gauged by their respective contributions towards reducing technical inefficiencies, which are represented by the distance of each country from the constructed frontier. Results from the multiple models examined in the paper indicate that inflows of foreign investment and trade have been instrumental in reducing inefficiencies across OECD countries, whereas outflows of foreign investment exacerbate inefficiencies. The study also confirms some previous findings that the spillover effects of FDI inflows are larger than that of trade but does not find evidence in favour of the view that the spillover effects of trade are overestimated when FDI flows are excluded from the analysis. Moreover, the impact of FDI inflows is larger than those of FPI and OFI inflows. The importance of absorptive capacities of host economies in capturing spillover gains from FDI inflows is also examined. Amongst the various measures of absorptive capacity considered, only human capital was found to be importantforeign direct, portfolio and other investment; spillovers; stochastic production frontier; OECD;

    CO2 lidar system for atmospheric studies

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    A lidar facility using a TEA CO2 laser source is being developed at the ENEA Laboratories for Atmospheric Studies. The different subsystems and the proposed experimental activities are described

    A post-Newtonian diagnosis of quasiequilibrium configurations of neutron star-neutron star and neutron star-black hole binaries

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    We use a post-Newtonian diagnostic tool to examine numerically generated quasiequilibrium initial data sets for non-spinning double neutron star and neutron star-black hole binary systems. The PN equations include the effects of tidal interactions, parametrized by the compactness of the neutron stars and by suitable values of ``apsidal'' constants, which measure the degree of distortion of stars subjected to tidal forces. We find that the post-Newtonian diagnostic agrees well with the double neutron star initial data, typically to better than half a percent except where tidal distortions are becoming extreme. We show that the differences could be interpreted as representing small residual eccentricity in the initial orbits. In comparing the diagnostic with preliminary numerical data on neutron star-black hole binaries, we find less agreement.Comment: 17 pages, 6 tables, 8 figure

    A stochastic-Lagrangian particle system for the Navier-Stokes equations

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    This paper is based on a formulation of the Navier-Stokes equations developed by P. Constantin and the first author (\texttt{arxiv:math.PR/0511067}, to appear), where the velocity field of a viscous incompressible fluid is written as the expected value of a stochastic process. In this paper, we take NN copies of the above process (each based on independent Wiener processes), and replace the expected value with 1N\frac{1}{N} times the sum over these NN copies. (We remark that our formulation requires one to keep track of NN stochastic flows of diffeomorphisms, and not just the motion of NN particles.) We prove that in two dimensions, this system of interacting diffeomorphisms has (time) global solutions with initial data in the space \holderspace{1}{\alpha} which consists of differentiable functions whose first derivative is α\alpha H\"older continuous (see Section \ref{sGexist} for the precise definition). Further, we show that as N→∞N \to \infty the system converges to the solution of Navier-Stokes equations on any finite interval [0,T][0,T]. However for fixed NN, we prove that this system retains roughly O(1N)O(\frac{1}{N}) times its original energy as t→∞t \to \infty. Hence the limit N→∞N \to \infty and T→∞T\to \infty do not commute. For general flows, we only provide a lower bound to this effect. In the special case of shear flows, we compute the behaviour as t→∞t \to \infty explicitly.Comment: v3: Typo fixes, and a few stylistic changes. 17 pages, 2 figure

    Magnetic behavior of nanocrystalline ErCo2

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    We have investigated the magnetic behavior of the nanocrystalline form of a well-known Laves phase compound, ErCo2 - the bulk form of which has been known to undergo an interesting first-order ferrimagnetic ordering near 32 K - synthesized by high-energy ball-milling. It is found that, in these nanocrystallites, Co exhibits ferromagnetic order at room temperature as inferred from the magnetization data. However, the magnetic transition temperature for Er sublattice remains essentially unaffected as though the (Er)4f-Co(3d) coupling is weak on Er magnetism. The net magnetic moment as measured at high fields, sat at 120 kOe, is significantly reduced with respect to that for the bulk in the ferrimagnetically ordered state and possible reasons are outlined. We have also compared the magnetocaloric behavior for the bulk and the nano particles.Comment: JPCM, in pres

    The Dirac Equation Is Separable On The Dyon Black Hole Metric

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    Using the tetrad formalism, we carry out the separation of variables for the massive complex Dirac equation in the gravitational and electromagnetic field of a four-parameter (mass, angular momentum, electric and magnetic charges) black hole.Comment: 13 page

    Detecting the limits of regulatory element conservation and divergence estimation using pairwise and multiple alignments

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    BACKGROUND: Molecular evolutionary studies of noncoding sequences rely on multiple alignments. Yet how multiple alignment accuracy varies across sequence types, tree topologies, divergences and tools, and further how this variation impacts specific inferences, remains unclear. RESULTS: Here we develop a molecular evolution simulation platform, CisEvolver, with models of background noncoding and transcription factor binding site evolution, and use simulated alignments to systematically examine multiple alignment accuracy and its impact on two key molecular evolutionary inferences: transcription factor binding site conservation and divergence estimation. We find that the accuracy of multiple alignments is determined almost exclusively by the pairwise divergence distance of the two most diverged species and that additional species have a negligible influence on alignment accuracy. Conserved transcription factor binding sites align better than surrounding noncoding DNA yet are often found to be misaligned at relatively short divergence distances, such that studies of binding site gain and loss could easily be confounded by alignment error. Divergence estimates from multiple alignments tend to be overestimated at short divergence distances but reach a tool specific divergence at which they cease to increase, leading to underestimation at long divergences. Our most striking finding was that overall alignment accuracy, binding site alignment accuracy and divergence estimation accuracy vary greatly across branches in a tree and are most accurate for terminal branches connecting sister taxa and least accurate for internal branches connecting sub-alignments. CONCLUSION: Our results suggest that variation in alignment accuracy can lead to errors in molecular evolutionary inferences that could be construed as biological variation. These findings have implications for which species to choose for analyses, what kind of errors would be expected for a given set of species and how multiple alignment tools and phylogenetic inference methods might be improved to minimize or control for alignment errors

    Trapped gravitational wave modes in stars with R>3M

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    The possibility of trapped modes of gravitational waves appearing in stars with R>3M is considered. It is shown that the restriction to R<3M in previous studies of trapped modes, using uniform density models, is not essential. Scattering potentials are computed for another family of analytic stellar models showing the appearance of a deep potential well for one model with R>3M. However, the provided example is unstable, although it has a more realistic equation of state in the sense that the sound velocity is finite. On the other hand it is also shown that for some stable models belonging to the same family but having R<3M, the well is significantly deeper than that of the uniform density stars. Whether there are physically realistic equations of state which allow stable configurations with trapped modes therefore remains an open problem.Comment: 10 pages, 3 figures, LaTeX2
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